Initially these inflammatory changes are completely reversible, but over the years irreversible changes start to take place —edema, scarring, and fibrosis build up, leading to thickening of the epithelial basement membrane, which permanently reduces the airway diameter.

最初这些炎症变化是完全可逆的，但是随时间进展，不可逆的变化开始发生，出现水肿、瘢痕、纤维化等症状，导致上皮基底膜增厚，从而永久性地减小气道直径。